The present invention relates to a combined force and kinetic energy measuring device and, more particularly, to a device for measuring elevator door-closing force and kinetic energy.
The American National Standard Safety Code ANSI A17.1-1978 for Elevators, Dumbwaiters, Escalators and Moving Walks, requires that powered horizontal sliding elevator doors be restricted in their motion by two rules. The first rule, number 112.4a, limits the total kinetic energy in the door system to seven (7) foot-pounds where a reopening device is used and two and one-half (21/2) foot-pounds where such a door reopening device is not used. The second rule, number 112.4b, limits the force necessary to prevent the closing of the door system to thirty (30) pounds measured at the leading edge of the door in the middle one-third of travel. The measuring of the force limitation is accomplished easily by a simple compression spring gauge. The measurement of the total kinetic energy of the door system has, however, been more difficult. The present prescribed method of determining the kinetic energy of the door involves measuring its average closing speed as described in rule 112.4a-1 and 2 and combining this with the mass of the door system in the formula: EQU KE=1/2MV.sup.2
where
KE=kinetic energy PA1 M=mass PA1 V=velocity
The problem is that the masses of the system are difficult to establish, since some are rotational and some linear, and they vary from elevator to elevator depending on the configuration and material used in the door system. It has historically been a problem to establish the mass of a specific system and therefore difficult for safety enforcement authorities to confidently confirm compliance with the rules.
In U.S. Pat. No. 2,163,847 of Perrey, a device for measuring the impact of an article of known mass is described. The device, which has a small inertial member also of known mass, is attached directly to the article whose impact is to be measured. The inertial member is attached to a precision calibrated spring and carries an indicator. When the article impact occurs, the inertial member's deflection is controlled by the spring and the size of the deflection is recorded by the indicator. The deflection is an indication of the kinetic energy of the inertial member and it is related to the kinetic energy of the article by the ratio of their masses. If this device were used to measure the kinetic energy of an elevator door, there would still remain the problem of calculating the mass of the door system.